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Allan Hills A77260
Basic information Name: Allan Hills A77260
     This is an OFFICIAL meteorite name.
Abbreviation: ALHA77260
This meteorite may also be called Allan Hills 77260 (ALH 77260) in publications.

Observed fall: No
Year found: 1977
Country: Antarctica [Collected jointly by ANSMET (US) and NIPR (Japan)]
Mass:help 744 g
Classification
  history:
Antarctic Meteorite Newsletter:  AMN 2(1)  (1979)  L3
Meteoritical Bulletin:  MB 76  (1994)  L3.5
NHM Catalogue:  5th Edition  (2000)  L3.5
MetBase:  v. 7.1  (2006)  L3.5
Recommended:  L3.5    [explanation]

This is 1 of 95 approved meteorites classified as L3.5.   [show all]
Search for other: L chondrites, L chondrites (type 3), Ordinary chondrites, and Ordinary chondrites (type 3)
Writeuphelp
Writeup from AMN 2(1):
This text was reprinted from AMN 2(1) in AMN 4(1). In some cases, it may be an updated version from the original.

Sample No.: ALHA77260

Location: Allan Hills

Field No.: 77123017

Weight (gms): 744.3

Meteorite Type: L3 (tentatively)

 

Physical Description:

The specimen is oblong 14.0x5.5x6.5 cm. A thin fusion crust, 0.5 mm, covers 50% of the specimen. There are several fractures that penetrate the stone and snow was preserved in these when it was removed from cold-storage. Light colored chondrules and lithic clasts, up to as much as 0.5 cm in maximum length, were observed on the fractured surfaces. Apparently the reddish-brown color of the weathering rind masks out the darker inclusion on the exterior surfaces. The meteorite appears to be weathered throughout.

 

Petrographic Description: Brian Mason

The section shows well-developed chondritic structure, chondrules ranging from 0.2-1.5 mm in diameter; some of the chondrules are irregular or broken. A variety of types is present, the commonest being barred olivine, granular olivine-pyroxene, and fine-grained radiating pyroxene. The barred and granular chondrules have interstitial glass, usually turbid and partly devitrified, but sometimes transparent and pale brown in color. Much of the pyroxene is polysynthetically-twinned clinopyroxene. The groundmass is fine-grained olivine and pyroxene, with minor subequal amounts of nickel-iron and troilite. Limonitic staining and occasional patches of limonite are present throughout the section. Microprobe analyses show highly variable composition for both olivine (Fa7-23, average Fa16) and pyroxene (Fs1-28, average Fs11). The highly variable composition of olivine and pyroxene indicates a type 3 chondrite, and the small amount of nickel-iron suggests L group, so the meteorite is tentatively classified L3; however, certain assignment should await further investigation.

Data from:
  MB76
  Table 2
  Line 211:
Origin or pseudonym:Main icefield
Mass (g):744.3
Class:L3.5
Weathering grade:C
Fayalite (mol%):7-23
Ferrosilite (mol%):1-28
Comments:26Al=37±2; 77011 pairing group
Catalogs:
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References: Published in Antarctic Meteorite Newsletter 2(1) (1979), JSC, Houston
Published in Meteoritical Bulletin, no. 76, Meteoritics 29, 100-143 (1994)
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Geography:

Antarctica
Coordinates:
     Catalogue of Meteorites:   (76° 43'S, 159° 40'E)
     Recommended::   (76° 43'S, 159° 40'E)

Statistics:
     This is 1 of 38937 approved meteorites from Antarctica (plus 5051 unapproved names)
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